December, ’20] WOGLUM AND HOUNDS: DAYLIGHT ORCHARD FUMIGATION 481 
tent with safety and without annoyance at the end of a 50-minute 
daylight exposure so little gas remained, but on the other hand this 
was seldom possible beneath the tannin-treated tents especially on the 
sunward side, because of the greater volume of residual gas. Particu¬ 
larly of interest is the tendency of the gas to remain strongest on the 
hot sunward side of the tree and to escape more freely from the 
cooler portions. 
As a possible explanation of this situation it can be stated that the 
sun falling on the tent produces a very rapid rise in temperature, 
which is greatest immediately beneath the cloth and decreases as the 
distance away becomes greater. The cyanid gas is cold when entering 
the tent at the lower and cooler part. As it diffuses with the air and 
rises the mixture comes in contact with the hotter air on the sunward 
side but appears to be retarded in escaping from the tent on this side 
by the very highly heated peripheral layer of air immediately adjacent 
to the cloth. Dark colored tenting intensifies the temperature of this 
layer. 
Table V— Temperature Comparison on Sunward Side of the Peripheral Layer of Air Inside 
Two Trees Covered Respectively with Light and Dark Colored Tents. Records Taken 
11 Feet Above Ground One Hour After Covering 
Light tent 
8-oz. army duck 
Dark tent 
6^-oz. drill 
Temp. 6-8 in. 
from cloth 
Temp, immedi¬ 
ately adjacent 
cloth 
Difference 
Temp. 6-8 in. 
from cloth 
Temp, immedi¬ 
ately adjac¬ 
ent cloth 
Difference 
106° 
118° 
12° 
114° 
142° 
28° 
The dark colored tent shows the remarkable difference of 28 degrees 
between the temperature immediately adjacent the cloth and that 
distant 6 to 8 inches; the white tent only 12 degrees. Records taken 
simultaneously at 3| feet on the shaded side of the tree gave tempera¬ 
tures of 92 and 85 degrees respectively for the dark and light tents. 
When these latter records are compared with those taken immediately 
adjacent the cloth on the sunward side there is presented the very 
great difference of 50 degrees between the extremes of temperature 
within the tannin-treated tent and 33 degrees within the white tent. 
The temperature of the air on the shaded or north side of the tree 
covered with the white tent almost paralleled that of the outside air 
and in the case of the dark tent was but 6 to 7 degrees higher. There¬ 
fore, the absence of a hot layer of air on the shaded side immediately 
adjacent to the tent allows the gas to diffuse outward as freely over 
this area as at night. 
